Digital signal processing methods, systems and computer program products are widely used to determine a signature or characteristic of a signal. The signal may represent, for example, an acceleration signal from an accelerometer that results from motion, and digital signal processing may be used to characterize the motion with a signature. The digital signal processing may be used in a training sequence, to characterize a given type of signal, and then may be used to compare the signature of a new signal to the signature(s) of the training signal(s), to thereby identify the new signal. Such digital signal processing may be used in many other applications, such as data mining applications, recognizing postures and gestures, entertainment, athletics, transportation, defense, safety, healthcare and many other applications.